I had gotten the preamp on ebay in ok condition. It needed a cleaning and had 1 previous owner from what I was told. It works, but I noticed intermittent issues with the audio. Sometimes one channel will go low and then back to normal. Also both channels don’t seem balanced. I’m getting it serviced at a certified mcintosh dealer, but they are saying to get everything serviced (recapping and new tubes) will run $900 or so. I was wondering if anyone had issues similar and if this would probably fix the issue? I have no experience in audio repair, so I wouldn’t feel comfortable doing anything myself. Thanks.
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Hi, welcome to AK and congratulations on your MX.
The problems you have can likely be solved by proper cleaning of the switch contacts and controls with the proper cleaning fluids. DeOxit is a popular cleaner and is good for cleaning fixed contacts (like the RCA connectors) but should not be used on the rotating controls. F5 FaderLube should be used for those and I like to use F5 on sliding switch contacts as well.
The problem is that oxidation causes a film to form on the contact surfaces that can interrupt electrical current. This thread might be helpful if you want to do that cleaning yourself: https://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/. As a temp measure, try working the switches a bit. Try moving the tape monitor switch on and off several times and the same with the source selector and other switches. Doing that may rub off some oxidation and fix the intermittent audio but also means the contacts should really be properly cleaned.
But having said that, the MX is like 60 years old and has electronic components (capacitors, resistors, etc.) with design lives of maybe half that time or less. So a restoration service is pretty much needed and recommended (unless such has been done to this unit recently). The service should include replacing many, most or all the capacitors, any resistors or other stuff that have drifted out of spec. and any bad tubes. I would not replace all the tubes, only those that don't test well. The service should also include complete cleaning of the switches, controls and contacts and proper alignment of the FM tuner. Note that tuner alignment requires a different set of skills and test equipment than the rest of this work and so you should find a tech that knows how to do that and knows old McIntosh tuners. The cost you mention is worth the price as your MX will come back being one of the sweetest sounding preamps out there and will work properly for a long time. (Although periodic cleaning of controls and switches will be needed.)
So which MX do you have? There are 3 versions that are described here: http://www.mcintoshcompendium.com/mp-tunerpre-amps.htm
What city / area are you in; which McIntosh service center are you planning to use.
Also, what power amp are you using?
Any pictures of your new find?
I have had channel dropouts from my MA230 and t has been an issue with the Tape Monitor rocker switch. If that is your issue, moving it back and forth can fix the connection. I don't think there is a replacement for the rocker switch, but I know some have had better luck rebuilding the switch. That sort of repair is beyond me, and I bet you would have a hard time finding a McIntosh dealer who wants to rebuild a rocker switch, but you never know.
Also, take a look at the tubes, particularly the the three 12AX7 and two 6U8 tubes clustered in the preamp section. Cleaning the sockets pins on the tubes and making sure they are all properly seated can help.
I would agree with the service center that you need a recap. It is well worth it. These machines really are wonderful pieces when working correctly!
Also, take a look at the tubes, particularly the the three 12AX7 and two 6U8 tubes clustered in the preamp section. Cleaning the sockets pins on the tubes and making sure they are all properly seated can help.
I would agree with the service center that you need a recap. It is well worth it. These machines really are wonderful pieces when working correctly!
Thank you. I have the late model mx110. I’m using a McIntosh 240 tube amp. I’m currently in Corpus Christi, tx, but having it serviced at Bjorns in San Antonio. I originally fell in love with having a vintage mcintosh set up, but lately I’ve been thinking of getting something newer to save me from having to replace parts that may not be made anymore. Before I jumped into the vintage gear, I was looking at the mcintosh 252 integrated amp.
Good combination. Maybe someone in TX can chime in with a review of Bjorns. Please post how things go.
Hello Everyone,
I am sorry to barge in but I have an MX110 and had it rebuilt recently. I was playing my vinyl and I noticed it started sounding distorted. I shut the system down and now try play vinyl and it just horrible distortion at low volume. I have been trying to find a tube layout for the phono section, but I can't. Any help would be appreciated on what the issue may be.
I am sorry to barge in but I have an MX110 and had it rebuilt recently. I was playing my vinyl and I noticed it started sounding distorted. I shut the system down and now try play vinyl and it just horrible distortion at low volume. I have been trying to find a tube layout for the phono section, but I can't. Any help would be appreciated on what the issue may be.
There are two 12AX7s that are located together, in-line front to rear, front of chassis center, and to the left of chassis center, mounted on their own little sub-plate that is isolated from the chassis. Those tubes are the two phono preamp tubes -- one for each channel. However, if the problem presented itself in both channels at once, it is doubtful that those tubes are the problem. This will most likely be a problem in something that is common to both channels: The power supply. If something in the power supply has failed so that (now) those tubes only receive a fraction of the voltage they need to operate properly, then that would account for the gross distortion, and it appearing in both channels at the same time.
Dave
Dave
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Also, if your issues are from the phono stage(s) or the AUX input, there are a series of 6 knobs on the top of the unit controlling these inputs that may be hidden by a wooden case. Many times these also need a deoxit treatment for optimal functioning...
The AK database has most all of what you need in service manuals and schematics....
MX110 Schematic.pdf (akdatabase.com)
Which version of the MX110 do you have?
I have an MX110 that is the early M version where the notation that identifies all the tubes is nearly worn off the chrome. This attached photo is essential to me so I know which tubes go in which sockets. The later versions are almost identical (a Z version has a 6D10 tube), but what is the same for both versions is the cluster of the 5 tubes, the 3 12AX7 and the 2 6U8 tubes towards the front that affect sound the most. If I start hearing static in my unit, I check to make sure that these tubes are seated well in their sockets. If it persists I will change them out one by one until I find one causing an issue. This has helped me on two occasions to get rid of static and noise.
I wish I could give the proper credit to the AK member who uploaded this photo. I don't remember who it was. After I got my MX110, when I would have issues with my the unit I would search on AK on and try to absorb all I could. It was from one of those threads that had this photo. So thanks to AK for helping me, and I hope it helps others.
